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[34.85.221.182]) by smtp.gmail.com with ESMTPSA id 00721157ae682-7d35f7e286esm321947b3.29.2026.05.21.12.40.19 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 21 May 2026 12:40:19 -0700 (PDT) From: Sean Paul To: intel-gfx@lists.freedesktop.org Cc: jani.nikula@linux.intel.com, Sean Paul , Rodrigo Vivi , Joonas Lahtinen , Tvrtko Ursulin , David Airlie , Simona Vetter , intel-xe@lists.freedesktop.org, dri-devel@lists.freedesktop.org Subject: [PATCH v2 1/2] drm/i915/color: Fix step discontinuity in Post-CSC Gamma LUT Date: Thu, 21 May 2026 15:39:44 -0400 Message-ID: <20260521194018.2445206-1-sean@poorly.run> X-Mailer: git-send-email 2.54.0.794.g4f17f83d09-goog In-Reply-To: <6d8e36e2aea806f9973b3c501aad4523f7316d6a@intel.com> References: <6d8e36e2aea806f9973b3c501aad4523f7316d6a@intel.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Mailman-Approved-At: Fri, 22 May 2026 14:41:05 +0000 X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" From: Sean Paul Fix a step discontinuity in the Post-CSC Gamma LUT when SDR dimming is active by clamping Segment 2 to the last user-provided LUT entry value instead of hardcoding it to 1.0 (1 << 24). Link: https://lore.kernel.org/intel-gfx/20260521180143.2143262-1-sean@poorly.run/ #v1 Signed-off-by: Sean Paul Changes in v2: - Split out into separate patches for pre/post csc fixes - Dropped loop bounds fix in favor of [1] [1]- https://lore.kernel.org/r/20260519075245.383864-1-pranay.samala@intel.com --- drivers/gpu/drm/i915/display/intel_color.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/drivers/gpu/drm/i915/display/intel_color.c b/drivers/gpu/drm/i915/display/intel_color.c index 2d318e922671..90d5dc2ef3e4 100644 --- a/drivers/gpu/drm/i915/display/intel_color.c +++ b/drivers/gpu/drm/i915/display/intel_color.c @@ -4023,11 +4023,11 @@ xelpd_program_plane_post_csc_lut(struct intel_dsb *dsb, lut_val); } - /* Segment 2 */ + /* Segment 2 - clamp to the last LUT value to prevent step discontinuity */ do { intel_de_write_dsb(display, dsb, PLANE_POST_CSC_GAMC_DATA_ENH(pipe, plane, 0), - (1 << 24)); + lut_val); } while (i++ < 34); } else { /*TODO: Add for segment 0 */ -- Sean Paul, Software Engineer, Google / Chromium OS